Creature Feature: Hoatzin


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Adult hoatzin. Photograph by Edison Buenaño

The Hoatzin (Opisthocomus hoazin), pronounced “wat-sen,” is one of the strangest and most fascinating birds around. With an appearance like a miniature dinosaur, the hoatzin is the only extant member of its taxonomic order, the Opisthocomiformes.  Hailing from South America, these prehistoric-looking birds are uniquely adapted to live in the swamps and mangroves of the Amazon.

Unlike most birds, the hoatzin is folivorous (a leaf eater) with over 80% of its diet comprised of leaves. Leaves are very fibrous and quite difficult for most animals to digest – so how does the hoatzin do it? The same way cows digest grass! They are the only known bird to use foregut fermentation. Basically, they break down the rough plant matter using bacterial fermentation before it travels to the gut for digestion. While this unique adaptation allows hoatzins to consume a food source that has little competition from other birds, there is a downside to their ruminant-like digestion: the smell. Their bacterial digestion leads to a distinct, cow-pie-like odor has even given them the nickname “stinkbird.”

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Hoatzin chick. Image found at:

Hoatzin chicks have a unique defense system suited to their dinosaur-like visage. Adult birds build nests in low-hanging branches over water. When threatened, adults, who breed in small groups, will mob the predator while the young attempt to hide in the foliage.  However, if discovered, the chicks will jump out of the tree into the water below and swim to the shore. After reaching safety, the chicks use claws on their wings (which disappear by adulthood) to climb back into the trees.  Though this adaptation is reminiscent of the fossil archaeopteryx’s own clawed wings, the hoatzin does not seem to share the ancient bird’s lineage, though the taxonomic placement of the hoatzin is still quite controversial.

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Archaeopteryx. Image from:
Hoatzin chick, with claws highlighted.  Image from Cornell lab of Ornithology.
Hoatzin chick, with claws highlighted. Image from Cornell lab of Ornithology.


Check out this video to see these crazy dino-claws in action!

One Comment Add yours

  1. Mikayla says:

    Does this bird also moo because it has a cow stomach. Is it similar to cows in any other way?


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